Torque controlling mechanism



Dec. 26, 1950 M. J. BURGER ET AL 2,535,667

TORQUE CONTROLLING MECHANISM Filed Nov. 10, 1949 4 Sheets-Sheet l 4 5 i /6 7 EAR TORQUE I MOTOP saw/rm: LOAD 2/ TRAIN COUPL/N6 22 o M J BURGER Q M a E LEME %2or RESPONSE MEASURED- BY 440101 OJ [.0 I0 I00 FREQUENCY IN CYCLES PER SECOND ATTORNEY Dec. 26, 1950 M. J. BURGER ET AL 2,535,557

TORQUE CONTROLLING MECHANISM Filed Nov. 10, 1949 4 Sheets-Sheet 2 9s- FIG. 8

FIG. 5 FIG. 7

.MJBURGER //v1//vr0/?sa ECLEMENT ATTOPA/EV Dec. 26, 1950 M. J. BURGER ET AL 2,535,667

TORQUE CONTROLLING MECHANISM Filed Nov. 10, 1949 4 Sheets-Sheet 5 .M. J BURGER /A/l/EA/TO/?$- G. E CLEMENT ATTORNEY Dec. 26, 1950 M. J. BURGER ET AL 2,535,667

TORQUE CONTROLLING MECHANISM Filed Nov. 10, 1949 4 Sheets-Sheet 4 .M. J BURGER ffa E CLEMENT A T TOP/VE V Patented Dec. 26, 1950 Michael J1 Burger, Murray" Hill, and George F. Clement; East Orange, N. J assignors to Bell Telephone Laboratories,

Incorporated; New

York, N .Y., a corporation'of" New York Application November 10, 1949, Serial No. 126,574

7 Claims;

This invention relates to a torque controlling and torque measuring apparatus;

one object of the inventionis an apparatus" producing clockwise, or counter-clockwise,- torques of" all values from zero to the maximum capability of a: prime" mover.

Another object'- of the invention is an apparatus producing clockwise, or counter-clockwise, torques proportional to a voltage;

Another object of the" invention is an apparatiisproduc'ing controllable clockwise, or coon-- tor-clockwise torqueswhich are independent. of the position o'rspeed of a driven shaft.

Another object of the invention is an apparatus=for measuring the torquesof torque produc i-hg" shafts regardless-of their speed or positions;

A feature of the invention is a' simple" and efficient device, substantially free of temperature elfec'ts, which directly measures the forces involved in the production of torques.-

In known torque determining apparatus,- such as the absorption dynamom'e'ter, arotar'ymember, such a's-- a shaft, is connected to the dynarnome'ter. The dynain'ometer absorbs'the output power of the rotary member bymechanical; hydraulic, or electric means, and usually converts this" output power into heat, though in some cases, a portion of the power is converted into u'sefur work. The dynam'or'net'er rovides some indirect indication; such as the pull on the lever arm of a prony brake or the current from a generator, by Whichthe torque may be determined. Readings are taken at various speeds, and from these readings, and simultaneous measurements of the corresponding speeds, the composite torque-speed characteristic is determined, and the power'output maybe evaluated. cSuch apparatus does not give direct readings of the forces producing the torques, is not readily reversible for the measurement of reciprocating or reversible torques, and cannot measure the torque of a stalled prime mover.

in" accordance with the present invention, a prime mover is connected through" a strain sensitive coup-ling toaload; The torque of the prime mover is controlled" by electrical-- means; and the strain sensitive coupling produces an electrical eir'ect which" is proportional to the stress producing the strain, and is therefore'proportional to the forceproducin'g' the torque;

This electrical eifect is fed back to oppose the electrical effect controlling the prime mover, thus compelling the prime mover to produce a torque of such magnitude that the'result'ant of these" two electrical effects will" cause the prime mover to produce the proper torque. As the electrical eflect' which is fed back is proportional tothe force producing the torque, this effect is a convenient measure of the torque.

In addition to measuring the torque transmitt'ed to a load, apparatusembodying the pres-- ent inventionmay be used to supply a measured torque to anelement rotated by some other source; regardless of its speed, to aid, or oppose, the torque due to this other source. Also, if the output shaft beheld against rotation, the apparatus will supply the required torque to the shaft within the limits of the prime mover.

The strain sensitive coupling may include two opposed discs, or crank arms, respectively afiixed to the shaft of the prime mover and the output shaft. One, or more, pins are mounted on" the driving disc and one or more pins onthe'driven disc, in overlapping relationship. One, or more, links, which may be in the form of flat Webs, interconnect the pins on the driving and driven discs and transmit the forces which produce the torque. A plurality of strain sensitive elements, such as resistance strain gauges, are mounted on these links to produce an electrical effect proportional to the strain in the links.

The invention will-be better understood from the attached drawings, in which:

Fig-,1 is-a block schematic of a system embodyingthe invention;

Fig. 2 is a detail schematic of the input connections to the amplifier of Fig. 1;

Fig.- 3 isa detail showing, partly schematic and partly diagrammatic, of the system of Fig. 1;

Fig. 4 shows certain characteristics of the sysitem shown in Fig; 3;

Fig. 5 is a side elevation of the motor and coupling of Fig. 3;

Fig. 6' is an end elevation of the apparatus of Fig. 5

Fig; 7 is a sectional detail of the attachment of the links to the concentric pin;

Figs. 8 and 9 show the attachment of a link to an eccentric pin;

Fig. shows a plan view in part section of the motor and coupling;

Fig. 11 shows an eccentric pin;

Fig. 12 shows a side elevation in part section of another strain sensitive coupling;

Fig. 13 shows a sectional elevation along the line 13-13 of Fig. 12; and c Fig. 14 shows the eccentric pins used in the coupling shown in Fig. 12.

In Fig. 1, a voltage applied through terminal I and resistor 2 to the input circuit of amplifier 3 controls the power supplied to motor 4 which drives, through gear train 5 and torque sensitive coupling 6, a load 1. The voltage developed by the torque sensitive coupling 6 is fed back through resistor 25 to the input circuit of amplifier 3 to oppose the applied voltage. A meter 8 reads the applied voltage and indicates the torque supplied to the load.

If the over-all loop gain'is high, the resultant voltage supplied to the input circuit of the am plifier 3 to control motor 4 is small, and the voltage fed back from the torque sensitive coupling is very nearly equal to the voltage applied to the terminal I, and indicated by the meter 8. Thus, by" applying an'appropriate voltage to the terminal I, the system will supply a desired torque to the load '5; If the load I is replaced by a torque producing device, the applied voltage may be ad justed to produce a torque whichcauses the torqueproducing device to'rotate at any desired speed. and the meter 8 will indicate the torque supplied. Any suitable speed indicating device, such as a tachometer or stroboscopa may be used to determine the speed of the output shaft.

y, In Fig. 2, the connections to the input circuit of amplifier 3 are shown in more detail.- The elements 2|, 22, 2 3, 24, are four resistance strain gauges embodied in the torque sensitive coupling 6. One pole, say the negative pole, of a grounded source of voltage (notshown) is connected by terminal 20 in series with the gauges 2|, 22. 23, 24. The junction of gauges 22, 23 is connected through the coupling resistor 25 to the input circuit of'amplifier 3. The opposite pole, in this case, .thepositive pole of a grounded source (not' shown) is connected by terminal 28 in series with adjustable resistor 21 and resistor 26 to the input circuit of amplifier 3, to send a current through elements 23, 2 3, opposing the current from thesource'connected to terminal 23, so that, by adjustment of resistor 21, the res ltant voltage drop across elements 23, 24, will initially be ofa suitable value to bias the amplifier 3. When'the elements 21, 22,23, 25 are strained. their resistr ances are changed, thus changing the voltage drcp across elements 23, 24 which is supplied to the input circuit of amplifier 3. A voltage ap plied to connection lfWill cause the motor to turn, straining the elements 2| 22, 23, 24 and producing a voltage which is supplied through resistor 25 to oppose the applied voltage.

In Fig. 3, the grounded source of voltage 30, having its poles connected to 'the winding of a potentiometer 3|, symbolically represents a controllable source of a voltage applied through terminal land resistors 2, 32. to the control electrode of the first section of a twin triode 33, incorporated in the amplifier 3. The'anodeof this first'section is connected to the control grid of the second section by an interstage network of the type disclosedinUnited States Patent 1,751 527, March 25, 1930, H; Nyquist. comprising resistors 34, 35, 35. anddecoupling resistor3'lf The anode of the second section is coupled by a similar net- 4 work comprising resistors 38, 39, 4!), and decoupling resistor 41, to the control electrode of the triode 32. The cathodes of the twin triode 33 are respectively grounded through self-biasing resistors 43, lid, which also supply local feedback.

The system may be energized by any suitable power supply (not shown) supplying positive potentials to terminals 28, 6-5, 16, c3, 52, and negative potentials to terminals 20, 41, 49.

The cathode of tube 42 is grounded, and the anode connected through the winding of relay 5! and. terminal 59 to the power supply (not shown). 1

A suitable grounded source of power 52 is connected to the swinger of relay 5! and. the contacts of relay 51 are respectively connected to ground through the windings of motor 4. A source of alternating voltage 53 is connected to the winding of potentiometer 5 3, and the brush of potentiometer 54 is connected through capacitor 55 to the control electrode of tube 55. The brush of potentiometer 54 is adjusted until, under no signal conditions, the swinger of relay 5i oscillates from one contact to the other contact, dwelling on each contact for substantially the same time. The positive potential is connected through terminal45, resistor 5%, adjustable resister 51 and resistor 43, to ground, so that, by adjustment of resistor 57, the potential of the cathode "of the first section of tube33 may be varied until, under no signal conditions, the swinger of relay 5! dwells for equal times on the relaycontacts, sending equal pulses of current through the motor windings. Under these conditions, the motor 1 may vibrate slightly but will not rotate. If the motor is not perfectly bal anced, then this control provides for balancing to obtain no motion. When a voltage from potentiometer 3| is applied to terminal I, the anode current of tube 52 will change, causing the swinger of relay 5! to dwell for a longer time on one contact and a shorter time on the other contact, thus sending unequal pulses of current through the windings of motor 4, and the motor 4 will develop torque in a direction determined by the polarity of the applied voltage, and will rotate at a speed determined by the amplitude of the applied voltage and the mechanical load.

The motor 4, through the gear train 5 drives the disc 60, facing the disc 6| attached to the output shaft. A stud. or crank pin 62, is secured to the disc 63 in overlapping relationship to one, or more. studs, or. crank pins. 63, 5 5, secured to the disc 6 l, and the pin 62 is connected to the pins 63. 64, by links 65, 65. The strain gauges 2|, 22 are mounted on the two sides of link 65, and the strain gauges 23, 24 are mounted on the two sides of the link 66, as the use of two gauges on each link increases the sensitivity of the coupling. The rotation of pin 62 with the disc will produce a tensional stressin one link, and a compressional stress in the other link, and these forces will cause the disc 5! to be rotated. The use of two sets of gaugesrespectively mounted on links undertension and under compression automatically compensates for a large part of the tem-' perature error of the strain gauges. To further reduce temperature eifec ts, the links may be made of material having a small temperature coeflicient, and the coupling may be encased to reduce the efiect of air draft.

The disc 80, or a di c'or cylinder associated therewith, is constructed to support three slip rings. 8B. 8!, 82. The terminal 20, connected to the power supply (not shown) is connected to the sausages? brusliassociated with the ring 8 connected to auge 21. Ground is c'onne'ctefi to the brush as:

24, and resistor is connected to the br'us-h as sdiat'etl with the ring" 82" connected to the jiiiicwhere is the sensitivity factor of the gauge.

The resistance of the gauge thusincreases linearly with increase, in length when: the gauge is under' tension, and decreases with decrease inlength; when-the gauge isunder compression:

In Fig-1 3; when-the'disc 60 is rotated counterclockwise'the link 65? and-gauges 212,- 2-2 will be under tension, while the link-66 and gauges 23, 2 4 will? be; under compression conversely, when the disc 60 is rotated clockwise; the link 65 andgauges 2l 22- will be under compression, while thelink: 65: and; gauges 23,; 24 will be" under compressionz: V v

In Fig. 2, let the volta e applied-toithe terminal- 2-0fbe' Eyand the voltage at the'junction of-gauges 22; 2-3Lebe 6o, initially; and er,- when thesystem: is transmitting a torque; Assuming thegauges are similar when. transmitting a torque, lathe-gauges 211. 22 increase in resistance, and gauges 2'3", 24" decrease in resistance, then;

4R a'ndth change de is given 59 d@::e,-'e,,=- 2 The strain;

dZ- s1tress Z' YA whereif i'siybungs modules f r" the mate-tar iiithe links 6016], and Ai ,isf the cross-sectional area of the nurse If 'I isthetorque,

The StI'BSS-TOOSB where; 1" is the radius at which the torque is transferred to" the links; and B' is" the angle be= tween the direction ofthe 'str'ess and the direcnon-or tangential force" producing the torque;

Substituting" iii Equation 2 2rYA cos-B T (3) Hence; the voltage fedback from the scram gauges; to" the-{ms circuit of amtii er is dire'btlyT propbrt'io'ii A to the" torque, thus the meter 8 may be" castrated m read directly in terms ofth'torquei; H v

The complete sys of' Fig. 3' forms a" feedback 169 which udes'the'motor 4" and gear train 5} and must be designed bythe usual methods applicab e tofeedback ystem; Ingone embodiment of the system of- Fig. 3, the phase margin andstability were improved b'y'th'e additiori or; resistor 58" and" capacitor 58 connected from the anodec'ircuit'to the control electrode of the second sectiomofi tube.- In Fig. 4, curve shows the estimated characteristic of the sys-' tem and curve L shows? the phase of the feedback system, indicating that the phase margin and gain margin; are adequate for stability. As shown by curve N, the calculated values of the response=speed characteristic are in satisfactory agreement-with the measured? values;

Themotor,- gear train' and torque sensitive coupling of Figs; 1 and- 3 is shownin detail in Figs. Etc-1'1": The-motor 4- is mounted-ona verticalplate 10;- supported by brackets H. The motor pinion meshes with the intermediate gear Sphavirig a shaft'journalled in the supports 12, 13,, united by the spacers 74,- and' supported by the plate 10 Apinion 76 onthe shaft supporting-gea'r 5-"mesh'es with gear teeth on the periphcry of the disc 60. The disc' 60' is secured to a sleeve" 'l-T- rotatably mounted by the ball bearings 15-" on a stub'shaft- IBsecured' to the plate- 10-: An insulating' disc 19, aflixed to the" sleeve 1-1; supports three-slip ringsBll', BI, 82; An insulating sheet 83-, ah'ixed to the support 1!]; supports nine brushes; of which eight brushes 84 to 9!, are shown. Three brushes bear on each slip ring to reduce the possibility" of malfunctioning of the apparatus due" to brush failure.

If discfi'l', which maybe in'the form of apulley ora-geams rotatably supported byball bearings 9l'- on the shaft-l8i and is suitablyconnected; as by a" belt, to any desired load.

For the most efiic'ierit utilizationof the strain gauges, these gauges should be" strained' to subs'tant'ially their maximum value when the ap paratus is transmitting full torque. In a unit, such a' s tiie present unit, in vvhich' the full torque is quite small; the webs of the connecting links must be rather thin, so that thestresses de velo'ped will strain these links, and the gauges aifixe'd' thereto',- to the desired extent.

Figs; '7, 8;-9, illustrate a convenient manner'of constructing the links. Corresponding recesses are formed irithe clamp plates 93, 94', and the web 92; which maybe formed of some thin ma teriar such as Duralumin, is stretched over the r lower plate; a short-length of rod is placed ontliesweb 92' in line'with' the recess, the upper plate is placed in position and the two clamp plates secured toge'ther'by any suitable means, such'asthe rivets 963' 91-. The plates'93, 94 may thenbe further secured; if desired, by other rivets. In order to distribute the stresses evenly across the width of the'web 92, it is necessary that the axis of the web 92'- be accurately located QO'd'egreesfrom the front edge of the plate 94. Corresponding holes are pierced in the plates 93; 94'; andthe-web-QZ, so that the-assembly may be slippedover the cr'ank pin 62 securedto the-disc 60-; As both link's 65',-66; are driven by the pin 62 toavoid interference between the links, a shotilder'is formed on the pin- 62- and a sleeve 98, resting on this shoulder, is interposed between the clamping plates 93, 94* and the oin' 62". The assembly may be'retainedin place by a wire 99 snapped into a groove in pin 62. As thin webs of this character cannot resist shearing stresses without tearing, the holes in the plates 93, 94 may bemadelarger than the pin62, or sleeve 98', so that only tensile stresses are applied to the web.

If the system be irreversible, that is, the'torque isalways in one direction, only one link would be necessary, and this link could be arranged always to be under tension; but, ina reversible system, two links are necessary, and, while one link under tension theother linkwillbe under the. equivalent .Tof I compression. I :As a thin web of this character cannot transmit any substan-, tial compressive -'stress'es, it' is necessary to con-' vert the compressive stresses into the equivalent of negative tensile stresses by prestressing the web to the center of the operating range, so that a tensile stress will increase the'stress' in-the web, while a compressive stress willreduce the stress'in the web. In such case;o'f course, the webs must have'at least twice the strength offa' single web which is only subjected to tensile stress. I j

The links 65, 66 may conveniently be p're stressed by making the pins 63, 64 eccentric, as shown in Figs. 10 and 11. The shank IOI is in: seited in a hole in'the disc 61', and'thepin'63 may be secured by nut IOI. Flats I02 are form'edxon the pin 63'so that a wrench may be applied to rotate the pin63' to any desired position-before the nut'IOI is tightened; The clamp'plates'on one end ofthe'link 65 are positioned on theportion I03, having an axis offset from the axis of the shank I00, and retained by the shoulder formed on the portion I03.

The strain gauges 2I,22, are mounted on the front and back of thelin'k 65, Fig. 6, connected in "series, and the free ends'connected to' terminals I05, I06 insulatingly mounted through the disc",60;rwhile the gauges 23, 24' are similarly mounted on the front and. ba,ck of the link 66 and connected .to-the, terminals I01,- I013. The

terminals I05, I06, I01, I08, are connected to the corresponding slipj rings '80,[8I, 82 ,Figs. 3, Sand 10.. V Figs. 12, 13, 14 show a strain sensitive coupling adapted for. the transmission of larger torques than. the coupling shown in Figs. to 10. The motor pinion'drives the gear disc- I whichis secured to the sleeveflIZI, mounted onthenpper ball race I22, secured by the retaining ring I23 threaded in the sleeve I2I. The lower ball race I24 is mounted on the shaft I26 and secured by the retaining ring I25 threaded onthe shaft I26. The sleeve I2I is shaped to form' a disc, or crank armacarrying the crank pins I21. The disc,.or crank arms I28 is keyed to the shaft I26 andfcarries the crank pins 129; in overlapping relationship with the pins I21. The shaft I26 is-rotatably mounted inball bearings. inthe end standards I30, I3I and is keyed to a coupling, such as the sleeve 132, driving the load. 1

The links I33, I34,.I35, I35 are shaped to have thin central webs, which may be secured, as by welding or brazing, to heavy end sections; orthe webs may be formed integrally with the end sec.- tions. The crank pins I21, I29, as shown in Fig. 14, have a shank I4I', which is bolted to the sleeve I2I, or the disc I28, a fiattenedQportion. I42, and two cylindrical portions I43, I44, defined by.

shoulders and having a common axis ofisetfrom gauges which are similarly strained connected inseries. To simplify the drawings, the slip rings and brushes have been omitted, but the slip rings may evidently be supported onthe disc I 28 andthe brush holder supported by the standard I3I. I I

For transmitting larger values of torque, the

diarneters. of the'op'posed discs,-'or"crank arms; and the number of crank-pins'maybe increased, withacorrespo'nding increase in the number-of strain gauges. T 7

;While a specific type of electric motor, and control circuit therefor, has been disclosed, the invention'is not limited thereby, but may be embodied in, many other systems using motors, elec tric; hydraulic, steam, heat or internal combustion, which may be controlled by a'suitable electrical control circuit.

What is claimed is:

1. A torque-producing apparatus, including a motor having a shaft, a source of control voltage,

' a circuit connecting said source and motorto control the energi'zation of said motor, a load, opposed crank arms'respectively attached to said motor shaft and said load and having overlap ping crank pins, links interconnecting the overlapping crank pins including electrical elements modified bythe transmitted strain to'p'roduce a voltage proportional to the torque transmitted tothe load, and connections for opposing the produced voltage to the control voltage, whereby the transmitted torque'ismade proportional to the control voltage, and is independent of the speed or position of theload.

2. The combination in claim 1 in which the control circuit includesa high gain amplifi'e'ix' "3fThe combinationin claim 1 in 'wliichthe opposed crank arms are shaped to form opposed discs.

4. The combination in claim 1 in which the links are flat webs and the strain sensitive elements are resistance strain gaugesadhe sively' as fixed to the webs.

5. The combination in claim 1 with means connected to the control circuit to indicate the produced torque. i

6. A torque-producing apparatus ,7 including a motor having a shaft, a source of control voltage, a. control circuit connecting said source and said motor, a load, opposed crank arms respectively connected to said motor shaft and said load and having overlapping crank pins, links having end sections perforated to fit oyer a pair of overlapping crank pins and webs connecting the end sections, resistance strain gauges adhesively secured to both sides of the webs, a second source of voltage connected to said gauges, and means connecting said gauges to said control circuit to oppose the voltage from said gauges to said control voltage.

7. A torque-producing apparatus including a motor having a shaft a source of control voltage, a high gain amplifier having an input circuit connected to said source and an output circuit controlling said motor,'a load, opposed crank arms respectively connected to said shaft and said load supporting overlapping crank pins rotatably secured to the crank arms and having projecting portions eccentrically located with respect to the remainders of the pins,1inks having end sections perforated to fit over a pair of overlapping crank pins and webs connecting the end sections, prestrained by rotation of the crank pins, resistance; strain gauges secured to both sides of the webs, a second source of voltage connected to said gauges, and means connecting said gauges tothe input circuit of said amplifier to oppose the voltage from said gauges to said control voltage. v V

MICHAEL J. BURGER. GEORGE F. CLEMENT.

No references cited. 

